Powertech MPPT controller - is it working as it should?

[Jill on Maya]

Am seeking help to diagnose whether our Powertech 30A MPPT controller model MP-3735 is working as it should.

This is our first solar installation.

We opted for two of these controllers for our new solar PV system for logical reasons. The unit ticks many boxes - MPPT, 65V OCV, 30A current, 360W array at 12V, no fan (quiet), compact size, programmable bulk and float voltages via screen menu, comprehensive display options, battery temperature sensor included, local supplier (Jaycar) so warranty is reliable and with all these features the price is good at $230.

System is 2 x 327 watt high end panels (Sunpower E20, 64.9 OCV), each wired using over spec cable to a separate controller and then to the house bank (3 x 225 Ah 12V Geltech gels). We liked the redundancy of two separate systems and the ability to compare performance. This has proved invaluable as three of the controllers have not worked properly. We knew each was faulty because we had a better performing controller to compare it with. Have just replaced the third faulty unit. Each unit has appeared to work on initial install and ceased working (0.00A on display) subsequently.

Internet research brings up some negative comment on the controller but this mostly relates to the units inability to perform in an unusual situation very unlike ours. However there is also a complaint that the unit is not really an MPPT controller and works more like a PWM controller. If this is true its very concerning as we want an MPPT controller to get the best from our panels.

On the last exchange we were offered an upgrade to a new model the Powertech MP3731 which is a 50A unit with max OCV of 95V. About $400 so upgrade is $170 each. Not keen to upgrade unless we know the MP3731 will perform better. To replace with these or any much larger units will require some more cabinet work.

We are in the higher latitudes (Tasmania) and summer is not here yet so we haven't had optimum solar conditions yet. The batteries are in good condition and we are maintaining full charge when both controllers are working. Maximum input we have seen on a controller screen has been 25A. Not bad for a 327 watt panel but we notice it fluctuates rapidly and widely jumping from 15A down to Min in stages and then back to 15A over a few seconds. I have read comments on this forum that suggests this indicates a not very sophisticated MPPT controller.

After 3 unit exchanges not surprising that we have lost confidence in their reliability and are now questioning their performance.

Can anyone suggest a way to assess the performance of the unit and whether it really does operate as an MPPT controller?

[smac999]

I don't see why you would spend the money on bigger controlers when then ones you have meet your spec. if these are having so many failures I would just spend that "upgrade" money on different ones of similar size instead.

[GILow]

Jill, I am a regular shopper at Jaycar, but I tend to avoid them for this sort of equipment. The symptoms you describe are all too familiar with the sort of budget friendly stuff Jaycar sells. I don't want to bag them, they are often very good value, but you might need to get beyond the value stuff for the job at hand.

I THINK Powertech is the generic inhouse brand that Jaycar uses for lots of stuff, so you really don't know what the solar regulator is under the cover. Maybe the multiple units are confusing one another in their attempts to multistage charge. Maybe they are a dud batch from whichever manufacturer made them. But I do think you will go crazy trying to get that level of electronic equipment working satisfactorily. And even if you do get something working, how long do you really think it will last?

In your situation I would be biting the bullet and going for one of the known brands of regulator.

But, your question was how to determine the performance of the units when they are working. For that I would use a decent quality shunt based battery monitor, something with real energy use accounting capability to get actual numbers of the energy being output from the controller. If you do not have one already it will be money well spent to get one. They are, I believe, a critical piece of electronic equipment on a boat

[GILow]

I'm going to go a little further and add the following remarks, they may or may not be worth consideration.

1. You mention that you are using gel batteries. Do these regulators REALLY understand the particular charging requirements of gel batteries because it is very, very easy to destroy gel batteries if the voltage gets too high.

2. You have spent big money on the panels. Compared to this I would have thought a decent regulator from a known manufacturer was relatively cheap. I use a very budget-friendly 420 watt regulator from Votronic which seems to have generally good reviews on the web, and has worked well for a number of years now, but at your level of panel I'd be thinking Outback or Morningstar or even Victron. But not Jaycar, sorry. And the Victron at least is less than $400 for your needs.

Matt

[GILow]

Oops. One MORE thing...

You mention that a bigger controller would need some cabinetry work...

That sounds almost as if the controllers are tightly enclosed in something. Please forgive me if I am stating the obvious, but these controllers are getting plenty of air flow, right?

[S/V Alchemy]

Originally Posted by GILow

Oops. One MORE thing...

You mention that a bigger controller would need some cabinetry work...

That sounds almost as if the controllers are tightly enclosed in something. Please forgive me if I am stating the obvious, but these controllers are getting plenty of air flow, right?

Bingo...yikes if the answer is "no, why?"

[soloauditor]

hi
mppt controllers do not like over voltage so you need to match the controller to the panel max voltage .that done ebay is a great source of cheap controllers i bought a fengsun which is a copy of the victron and i am very happy with it .Having the panels on seperate controllers sort of defeats the purpose of the more expensive mppt controller. i would put the panels in series and buy a 150 volt controller for 200 dollers .job done

[GILow]

Originally Posted by soloauditor

hi

mppt controllers do not like over voltage so you need to match the controller to the panel max voltage .that done ebay is a great source of cheap controllers i bought a fengsun which is a copy of the victron and i am very happy with it .Having the panels on seperate controllers sort of defeats the purpose of the more expensive mppt controller. i would put the panels in series and buy a 150 volt controller for 200 dollers .job done

A couple of things with this.

eBay is a great source of cheap and crappy controllers. The OP bought good panels, the output (and therefore value) of the panels is diminished by using a cheap controller.

Also, the OP is in Australia and is quoting Australian dollars. I can assure you that the cost of a decent 30 amp controller in Australia is going to be closer to AU$400. I did the numbers on importing decent controllers to Australia and, surprise, surprise, the costs are about the same as buying from a reputable importer. Then you get the whole parallel import warranty box of worms.

I think the OP is on the right track with the twin controllers. They'd need to buy a single 60 amp controller to mange those panels to their full potential and that's starting to look like big $ in one device. Plus the dual controllers means redundancy which is a very good thing on a boat IMHO.




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[mitiempo]

To answer your question I would install a shunt type ammeter. Ideally a true battery monitor - the Victron BMV-700 for example. This will show amps into the battery bank at any given time as well as cumulative amp hours over a period of time. After checking one controller move the shunt to the other.

It does sound like the controllers are not working properly.

As stated above they do need good airflow.

I agree with the 2 controller install and would do the same.

The OCV of the panels is very close to the maximum voltage of the off brand controllers you are using.

The only controllers I would use are name brand - Victron, Morningstar, or Outback the three that come to mind.

For example a Victron 100/30 MPPT controller will accept panel(s) of up to 100 volts. Every parameter is adjustable, not just voltages. This would be a good match in your situation.

[Barra]

Ive had one of these controllers for around 18 months now and no problems with it per say.

Its one of 2 MPPT controllers im using to run 2 seprate arrays. The other being a bluesky 15 amp for the smaller array. Its got one edge over the 15 amp one in that its far easier to adjust voltage setting for battery types etc.

The problem i have is the 2 controllers sense each others charging volts on the battery and one goes to float too soon but that doesnt sound like your issue.

I would doubt you have had 3 duds in a row and would look at the wiring set up personally and how the 2 units are interacting. simple first check would be wire the "dud" controller to the spot where the good one is - is it still a "dud"?

a hand held ampmeter is a very handy tool for doing these jobs - you can check amps in from panels, amps out and if the controller has managed to increase current like its supposed to etc

[Bruce K]

I have two of these Jaycar controllers. One controlling 2 Sharp panels 185W each and one controlling 2 200w sunpower flexible panels, all flat mounted, have been operating well foe over 18 mths. Occasionally need to be reset by disconnecting from batts via circuit breaker BK

[Jill on Maya]

Thank-you for all the responses. So much to consider.

First re the ventilation. The units are fitted on a bulkhead with plenty of airflow, no direct sun and the boat is in Tasmania so heat should not be a problem at this time of year. But it is to keep an eye on. The fitting instructions require space "on each side" for air circulation but they are designed to be mounted direct to a vertical surface so the only space behind is the few mm allowed for inside the casing. We could add a spacer to increase ventilation but there is no indication that failures to date have been due to overheat. They are warm not hot when charging.

Having 2 arrays and 2 controllers has enabled a swap as suggested by Barra. It was a swap that confirmed failure of two of the three units.

Yes re the OCV at 64.9V is close to the controller max of 65V but the max power 327 watt is well within the 360 watt of the controller. Am I correct to say that when current is flowing voltage will never be close to OCV?

We have a Bogart Trimetric 2030 battery monitor. It is the discrepancy between its readout and the controllers that has increased our concern that the Powertech MP-3735 may not be reliable. The most recent replacement controller (the fifth unit) was only fitted three days ago so not much data yet to draw conclusions from. Our batteries are in good condition, we are not using much power at present and the controllers have moved to FLOAT each morning after only a few hours of solar input - just as expected.

However the Trimetric battery monitor display has shown input amps considerably higher than the combined totals showing on the 2 controllers and at other times the opposite - input amps much lower then the combined totals. These readings being when there is no other charging source and allowing for the minimal load (about 1.5A) when everything non essential is off.

These discrepancies, added to the 3 failed units have lead to our concern that the controllers are not the reliable, highly efficient MPPT controllers we want to match our efficient panels. GILow's comments reinforce these concerns.

GILow says "Maybe the multiple units are confusing one another in their attempts to multistage charge. Maybe they are a dud batch from whichever manufacturer made them. But I do think you will go crazy trying to get that level of electronic equipment working satisfactorily. And even if you do get something working, how long do you really think it will last?" Grrrr! We've already had to replace 3 units.

This raises the possibility that the units lack the sophistication to work efficiently when two controllers are charging a single battery bank. Barra says "The problem i have is the 2 controllers sense each others charging volts on the battery and one goes to float too soon" - is that what we can always expect with 2 controllers charging 1 bank or only with poor quality/ less sophisticated controllers?

What do we do now? Wait for another failure which might be outside the 12 month warranty or while on a passage? I'd like to return these for refund so we can invest in better quality units. Unfortunately Jaycar don't carry any of the brand names mentioned - Outback, Morningstar, Victron.
This brings me back to my initial question - is there a way to show that the controllers do not meet their advertised performance standard "uses the latest MPPT technology at all times which gives the maximum available output of the solar module". Perhaps Jaycar will allow refund without such proof. At this point we are certainly glad we purchased from local supplier.

Thanks for suggested alternatives. I will take a closer look at the Victron 100/30. I thought that charging profiles on the Victron could only be done by selecting one of the programmed options rather than entering bulk and float separately. Not so says Mitiempo. And does it have a display? It would seem a retrograde step to have only limited option dip switches and no display on the units.

[GILow]

You have a good battery monitor. So do you feel up to the task of a temporary rewire of the monitor shunt so that it only measures the power output by a single controller? If so, there's your solution. Just move the shunt so it measures the output of one controller, collect a day or two of data and compare this output with (a) your expectations, and (b) the stated output of the regulator. Easy. Repeat for the other controller.


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[daletournier]

Sort of related. On the boat I just purchased there is a jaycar powertec 20amp charger. Im not conviced mine is not faulty, dosent seem to go into float mode. During the day seems to sit around 14.3v constantly. I think people buy them because they are cheaper?

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[GILow]

Originally Posted by daletournier

Sort of related. On the boat I just purchased there is a jaycar powertec 20amp charger. Im not conviced mine is not faulty, dosent seem to go into float mode. During the day seems to sit around 14.3v constantly. I think people buy them because they are cheaper?

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Do you find it takes about five minutes just to sense the voltage?


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